.First an important disclaimer: I do not know. I really don't have any actual facts here.

Next, some fun speculation: It sure looks to me like a custom molded one-piece ring, it seems to change cross section and take the sharp turns without distortion. If it was standard catalog stock from somewhere I would expect a constant cross section. My guess is that they shoot it as chopped fiberglass with gel coat, or perhaps compression mold it from sheet molding compound.

I have used something similar on softening edges on young-un friendly display vehicles we call it rubberised bullnose profile (although its EPDM) we can get it upto 50mm wide, but it loses its flexibility in the larger profiles.the supplier we use has branches in the US https://www.rehau.com/us-en/furniture/e ... e/bullnosethey might be able to find you something.